Among thermoplastic resins, a polyester-series resin (such as a polybutylene terephthalate), a styrenic resin, or the like has excellent mechanical and electrical properties, weather resistance, water resistance, and resistance to chemicals and solvents. Therefore, the resin has been utilized for various purposes such as electric or electronic device parts, and automotive parts. While, these resins are required to have improved flame retardancy as the field of their uses expands.
Japanese Patent Application Laid-Open No. 287960/1986 (JP-61-287960A) discloses a process for injection molding a polyamide resin with improving moldability of the resin, which comprises adding a polyester-series resin having a butylene naphthalate unit to a polyamide resin having a xylylene adipamide unit. Japanese Patent Application Laid-Open No. 201963/1987 (JP-62-201963A) discloses a polyester resin composition of which gas barrier property and transparency are improved by adding a metaxylylene group-containing polyamide resin and a compatibilizing agent to a thermoplastic polyester resin. Further, Japanese Patent Application Laid-Open No. 92667/1988 (JP-63-92667A) discloses a resin composition for stretch blow molding which comprises a polyester resin having an ethylene terephthalate unit, a metaxylylene group-containing polyamide resin, and a specific thermoplastic resin, and additionally a mica powder. In these literatures, moldability, gas barrier property or transparency of resins is improved, however, flame retardant thereof is insufficient.
Therefore, there has been proposed a method for imparting flame retardancy to a thermoplastic resin by adding a flame retardant comprising a halogen-containing compound or an antimony-containing compound to the resin. For example, Japanese Patent Application Laid-Open No. 150349/1988 (JP-63-150349A) discloses a resin composition to which flame retardancy is imparted by blending a glass fiber, an organic halogen-containing flame retardant, antimony trioxide, and a hydroxide of an alkali metal or alkaline earth metal to a mixed resin comprising a polyamide resin and a nylon 66. However, the halogen-containing flame retardant is not preferable for environmental reasons because the flame retardant sometimes generates a dioxin-series compound on resolution caused by combustion. Therefore, there is proposed a method for rendering a resin flame-retardant by using a phosphorus-containing or nitrogen-containing compound as a halogen-free flame retardant.
Japanese Patent Application Laid-Open No. 25506/1994 (JP-6-25506A) discloses a flame-retardant resin composition in which a phosphorus-containing compound is added to a thermoplastic resin composition containing a copolymer of an aromatic vinyl compound and a vinyl monomer, a graft copolymer with or using a rubber-like polymer, and a novolak resin. Japanese Patent Application Laid-Open No. 111059/1997 (JP-9-111059A) discloses a flame-retardant resin composition in which to a polyolefinic resin is blended a certain amount of a phenolic resin, a phosphorus-containing compound (red phosphorus) and an expansive graphite. Moreover, Japanese Patent Application Laid-Open No. 195283/1998 (JP-10-195283A) discloses a polyester resin composition to which flame retardancy is imparted with the combination use of a phosphoric ester having a specific structure and a suitable amount of specific compound(s) (a novolak phenol resin, and an oxide of iron, cobalt, nickel or copper). Japanese Patent Application Laid-Open No. 152402/1999 (JP-11-152402A) discloses a flame-retardant polyester resin composition which comprises a polybutylene terephthalate, a reinforcing component, and a flame retardant composed of an aromatic phosphate oligomer and a melamine pyrophosphate.
The halogen-free flame retardant does not comprise harmful halogens, however, it is inferior to a halogen-containing flame retardant in flame retardancy, so that it is necessary to add a large amount of the flame retardant. The addition of a large amount of the flame retardant brings about bleeding out (blooming) and deterioration in mechanical properties of a resin. Therefore, it is impossible to improve mechanical properties along with flame retardancy. For example, in the case using an expansive graphite in combination with the flame retardant, the resin significantly deteriorates its external appearance on molding. In particular, use of a phosphoric ester as a phosphorus-containing compound brings about bleeding out or deterioration in thermal stability of the resin, and causes considerable decline in physical property of the resin due to hydrolysis.
Thus, in conventional methods, it is difficult to render a resin high flame-retardant without deteriorating properties of the resin. Moreover, the above-mentioned flame retardant is capable of imparting flame-retardant to a specific resin, however, it is impossible to render a wide variety of thermoplastic resins flame-retardant.
It is therefore an object of the present invention to provide a halogen-free flame-retardant resin composition which is rendered flame-retardant to a satisfactory level with the use of a small amount of a flame retardant, and a process for producing the same.
It is another object of the present invention to provide a flame-retardant resin composition in which mold deposit and bleeding out (or blooming) of a flame retardant is effectively inhibited and to which high flame retardancy is imparted without deteriorating properties of the resin, and a process for producing the same.
It is still another object of the present invention to provide a flame-retardant resin composition in which hydrolysis is inhibited even in the case using a monomeric phosphoric ester or polymeric phosphoric ester as a flame retardant and which is rendered flame-retardant to a high level, and a process for producing the same.
It is a further object of the present invention to provide a shaped article having improved flame retardancy.